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POAVR Butterfly - Timer reuse after internal oscillator calibration
 

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  1. POAVR Butterfly - Timer reuse after internal oscillator calibration
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    <p>I am calibrating the AVR Butterfly internal oscillator for being able to use USART, based on the sample code provided by AVR (see code below). As I also wanted to use two timer-controlled servo motors, I am wondering whether it is possible to reuse 16-bit timer 1 after the calibration process - I tried resetting the TCCR1A/B but it did not work out (code also below). I hope you can help me out with this.</p> <pre><code>void OSCCAL_Calibrate(void){ unsigned char calibrate = 0; int temp; unsigned char tempL; CLKPR = (1&lt;&lt;CLKPCE); // set Clock Prescaler Change Enable // set prescaler = 8, Inter RC 8Mhz / 8 = 1Mhz CLKPR = (1&lt;&lt;CLKPS1) | (1&lt;&lt;CLKPS0); TIMSK2 = 0; //disable OCIE2A and TOIE2 ASSR = (1&lt;&lt;AS2); //select asynchronous operation of timer2 (32,768kHz) OCR2A = 200; // set timer2 compare value TIMSK0 = 0; // delete any interrupt sources TCCR1B = (1&lt;&lt;CS10); // start timer1 with no prescaling TCCR2A = (1&lt;&lt;CS20); // start timer2 with no prescaling while((ASSR &amp; 0x01) | (ASSR &amp; 0x04)); //wait for TCN2UB and TCR2UB to be cleared delayMs(1000); // wait for external crystal to stabilise while(!calibrate) { cli(); // disable global interrupt TIFR1 = 0xFF; // delete TIFR1 flags TIFR2 = 0xFF; // delete TIFR2 flags TCNT1H = 0; // clear timer1 counter TCNT1L = 0; TCNT2 = 0; // clear timer2 counter while ( !(TIFR2 &amp; (1&lt;&lt;OCF2A)) ); // wait for timer2 compareflag TCCR1B = 0; // stop timer1 sei(); // enable global interrupt if ( (TIFR1 &amp; (1&lt;&lt;TOV1)) ) { temp = 0xFFFF; // if timer1 overflows, set the temp to 0xFFFF }else { // read out the timer1 counter value tempL = TCNT1L; temp = TCNT1H; temp = (temp &lt;&lt; 8); temp += tempL; } if (temp &gt; 6250) OSCCAL--; // the internRC oscillator runs to fast, decrease the OSCCAL else if (temp &lt; 6120) OSCCAL++; // the internRC oscillator runs to slow, increase the OSCCAL else calibrate = 1; // the interRC is correct TCCR1B = (1&lt;&lt;CS10); // start timer1 } } void motorInit(){ // reset timer 1 TCCR1A = 0; TCCR1B = 0; // initialize Servo Pins DDRB |= (1&lt;&lt;PB5) | (1&lt;&lt;PB6); ICR1H = ICR_VALUE &gt;&gt; 8; ICR1L = ICR_VALUE &amp; (TOP_VALUE); // reset OCRs setServoSpeed(0, 0); setServoSpeed(1, 0); // Set Timer mode (PWM Phase &amp; Freq. correct, clear on compare match) // and prescaler (8) TCCR1A = ((1&lt;&lt;COM1A1) | (1&lt;&lt;COM1B1)); TCCR1B = ((1&lt;&lt;WGM13) | (0&lt;&lt;CS12) | (1&lt;&lt;CS11) | (0&lt;&lt;CS10)); } </code></pre>
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